The present invention relates to lamps and assemblies incorporating the lamps, and more specifically, to an assembly comprising an external reflector and an electric lamp having an internal reflector for redirecting light to provide more efficient operation.
Ordinary lamp assemblies comprise a lamp, an external reflector for redirecting light emitted from the lamp in a desirable manner, and a housing surrounding the lamp and external reflector. Conventional single-ended electric lamps are inefficient in that significant portions of radiated light energy are lost. In a conventional incandescent lamp, for example, light energy radiating in the direction of the base of the lamp may be misdirected by the filament bridge and lost, or absorbed at the base of the lamp and converted into heat energy. Damage to the base of the lamp by such heat absorption is a significant cause of failure of conventional lamps.
Particularly in the case of use in theater, television, and architectural lighting, a high intensity, controlled beam of light is required. Concave external reflectors are ordinarily used in conjunction with conventional lamps to capture and redirect emitted light into a usable, controlled beam. Currently available external reflectors are typically shallow and of wide diameter relative to their depth. This is because the most efficient conventional external reflector design requires placement of the lamp filament as far as possible from the base of the reflector. This point is calculated to be the focal point of the lighting fixture. Conventional lamps must be placed with the filament near this focal point for the reflector to capture and redirect as much of the light emitted from the back of the filament and towards the base of the reflector as possible.
A significant disadvantage of this type of lamp assembly wherein the lamp filament is placed close to the mouth of an external reflector is that a portion of the light emitted from the filament is not captured and redirected by the external reflector, but rather is emitted forward of the reflector in an uncontrolled manner, failing to contact the external reflector at all. This uncontrolled light may also contact the interior of the lamp assembly housing and be absorbed as heat.
To overcome these deficiencies, secondary devices such as alternative filament designs or specialized external reflectors are often used to redirect the light path into the desired configuration. Such devices are disclosed, for example, in U.S. Pat. No. 5,268,613 to Cunningham and 5,466,981 to Fields et al., and are generally believed to be effective for their intended purpose. However, specialized filaments such as are disclosed by Cunningham, or integrated external reflectors such as are disclosed by Fields et al. do not wholly solve these problems and are complex and expensive to manufacture, thereby increasing the overall capital cost of the lighting fixtures incorporating them.
One solution for solving certain of the above problems relating to loss of light directed at the base of a lamp has been to include an internal reflector within the envelope of the lamp. For example, U.S. Pat. No. 5,535,111 to Wedell claims a lamp assembly comprising the combination of a housing, a lens affixed to the housing, a first (external) reflector supported by the housing, and a lamp located conventionally within the first reflector and housing. The lamp of U.S. Pat. No. 5,535,111 includes a second (internal) reflector having an outer edge adjacent the lamp envelope. Disadvantageously, this lamp design specifically requires placement of the second reflector in the lamp envelope in substantial alignment with the base of the first reflector to minimize passage of light into the base of the housing, essentially serving as a plug for the aperture in the base of the housing through which the lamp extends. Additionally, the base of the first reflector requires a downwardly protruding lip which surrounds the lower portion of the lamp, further reducing transmission of light into the base of the housing. Accordingly, the lamp of U.S. Pat. No. 5,535,111 must be placed in a specific orientation relative to the external reflector used, and further requires a specialized external reflector to maximize the amount of light recovered and emitted.
Therefore, there remains a need in the art for a lamp for use in situations requiring high intensity, controlled light beams which recovers and redirects substantially the entirety of the light energy emitted from the filament towards the base of the lamp and external reflector. There is also a need for a lamp which minimizes the amount of light lost at the mouth of the external reflector. Advantageously, the novel lamp described herein utilizes an internal reflector placed adjacent the filament, typically less than about an inch and more typically between about an inch and one-half inch from the filament, to redirect at least a portion of the light emitted from the filament back through the filament where a portion thereof is absorbed as heat energy, reducing the amount of electric current required to heat the filament to a desired operating temperature, and a portion thereof is emitted as useful visible light energy, thereby improving the efficiency of the novel lamp.
It will be appreciated by those of skill in the art that this novel lamp design eliminates the need to place the internal reflector in substantial alignment with the base of a specially designed external reflector while still allowing recapture and redirection of substantially the entirety of the light emitted from the filament towards the base of the lamp. Placement of the internal reflector adjacent to the lamp filament also allows orientation of the lamp relative to an external reflector such that the lamp filament, and therefore the focal point of the lamp assembly, is placed in closer proximity to the base of the external reflector than is possible with conventional lamp designs. This allows recapture and redirection of significantly more light than with conventional lamp designs regardless of the external reflector used.
The lamp of the present invention may therefore be used with any conventional external reflector, rather than requiring a specialized external reflector as is described in U.S. Pat. No. 5,535,111 to Wedell. However, the ability to place the lamp filament and therefore the focal point of a lamp assembly in close proximity to the base of an external reflector, rather than near the mouth of the external reflector as in conventional designs, also allows greater flexibility in the types of external reflector designs possible. The lamp of the present invention use of external reflectors which are of significantly narrower diameter than conventional reflectors. Smaller, less bulky lamp assemblies are therefore possible, without sacrificing efficiency of the lamp and intensity of the light beam emitted.
In accordance with the present invention, a lamp for producing light from an electric current supplied from an external source is provided. The lamp includes an envelope, a filament disposed within the envelope for producing the light, at least two filament supports, a base supporting the envelope and the filament supports having at least two contacts for supplying the electrical current from the external source to the filament, and a reflector disposed within the envelope for redirecting a portion of the light through the filament. Advantageously, the internal reflector reduces the electric current required to heat the filament to an optimum temperature for producing the light and maintain that temperature.
The internal reflector may be constructed of glass, ceramics, metal or any suitable material capable of efficiently reflecting heat and light energy, and capable of withstanding the internal operating temperatures of, for example, an incandescent or halogen cycle lamp. The internal reflector may be generally convex, concave, or planar in shape or a combination thereof so long as a sufficient amount of light required to heat the filament to an optimum temperature is redirected onto the filament. In one embodiment of the present invention, the internal reflector may be substantially concave for redirecting a significant portion of the light directly onto the filament. In another embodiment, the internal reflector may be further shaped such that a redirected portion of light not impinging on the filament combines with and emanates from the envelope in substantially the same direction as a remaining portion of light produced by the filament.
The internal reflector may be supported by a bridge attached to the filament supports between the base and the filament. In another embodiment, support for the internal reflector may be achieved using the filament supports or even separate support wires. The internal reflector may be positioned less than one inch from the filament, and preferably between about one inch and one-half inch from the filament. Positioning the internal reflector in this manner redirects light and heat energy away from the base of the lamp, thus reducing the exposure of the base to heat and recapturing light energy which may have been lost as described above.
A lamp assembly in accordance with the present invention includes the lamp described above, an external reflector, and a housing. The external reflector has an aperture in a first end thereof through which the lamp extends and a second end through with the light produced by the lamp is directed. The external reflector may be configured to extend in a substantially symmetrical fashion about a central longitudinal axis, and form a conical shape flaring outwardly from the aperture in the first end to the second end. Preferably, the external reflector prevents light produced by the filament from contacting and heating the housing which supports the lamp and the external reflector. Advantageously, this prevents overheating allowing the lamp assembly to be handled, even during long periods of operation.
In accordance with the method of the present invention, an electric current may be provided to a filament positioned within an envelope of the lamp. The filament radiates light in all directions and the filament is heated by reflecting at least a portion of the radiated light onto the filament. In this manner, the efficiency of the lamp may be improved by reducing the amount of electric current required to heat a filament to an optimum temperature for producing the light.
The method of reducing the amount of electric current required to heat a filament to an optimum temperature for producing light may include the additional step of supporting a substantially concave reflector in an envelope of the lamp adjacent the filament for reflecting a significant portion of the radiated light on the filament whereby the focal point of the light is the filament. Preferably, the reflector utilized in the supporting step is shaped such that the redirected portion of the light combines with and emanates from the envelope in substantially the same direction as a remaining portion of the light radiating from the filament. The reflector will typically be positioned between about one inch and one-half inch from the filament.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.